Catheters, particularly intravenous (IV) catheters, are used for infusing fluid (such as normal saline solution, various medicaments, and total parenteral nutrition) into a patient, withdrawing blood from a patient, or monitoring various parameters of the patient's vascular system. Peripheral IV catheters tend to be relatively short, and typically are on the order of about two inches or less in length. The most common type of IV catheter is an over-the-needle peripheral IV catheter. As its name implies, an over-the-needle catheter is mounted over a hollow introducer needle having a sharp distal tip. At least the distal portion of the catheter tightly engages the outer surface of the needle to prevent peelback of the catheter and thus facilitates insertion of the catheter into the blood vessel. The catheter and the introducer needle are assembled so that the sharp distal tip of the introducer needle extends beyond the distal tip of the catheter with the bevel of the needle facing up and away from the patient's skin.
In operation, the catheter and introducer needle assembly is inserted at a shallow angle through the patient's skin into a blood vessel. There are many techniques for inserting such a catheter and introducer needle assembly into a patient. In one insertion technique, the introducer needle and catheter are inserted completely into the blood vessel together. In another technique, the introducer needle is partially withdrawn into the catheter after the initial insertion into the blood vessel. The catheter is then threaded over the needle and inserted completely into the blood vessel.
To verify proper placement of the catheter in the blood vessel, the clinician confirms that there is flashback of blood in a flashback chamber. The flashback chamber is typically formed as part of the introducer needle hub. Once proper placement of the catheter into the blood vessel is confirmed, the clinician applies pressure to the blood vessel by pressing down on the patient's skin over the blood vessel distal of the introducer needle and the catheter. This finger pressure occludes or at least minimizes further blood flow through the introducer needle and the catheter. The clinician then withdraws the introducer needle, leaving the catheter in place, and attaches an appropriate device to the catheter. Such a device can include a fluid delivery device, a PRN device (pro re nata—i.e., “as the circumstances may require”), a deadender cap, or a blood pressure monitoring probe. Once the introducer needle is withdrawn from the catheter, the introducer needle is a blood contaminated sharp and must be properly handled and disposed of.
In recent years, there has been great concern over the contamination of clinicians with a patient's blood and recognition that blood contaminated sharps must be properly handled and disposed of to avoid an accidental needle stick. This concern has arisen because of diseases such as HIV and hepatitis, which can be transmitted by the exchange of body fluids from an infected person to another person. Contact with the body fluid of an infected person must be avoided. If an introducer needle has been used to place a catheter in a blood vessel of an infected person, the introducer needle, via its sharp distal tip, is a vehicle for the transmission of the disease. Although clinicians know of the need to properly handle blood contaminated sharps, unfortunately in certain medical environments, such as emergency situations or because of inattention or neglect, needlesticks with a contaminated introducer needle can still occur.
Because of the problem of accidental needlesticks by blood contaminated sharps, various types of needle shields have been developed. Generally, such needle shields work for their intended purpose but could be improved. For example, some needle shields are bulky, difficult to use, require special features or techniques to be operative, or may leave the sharp distal tip exposed after use until the clinician manually activates the needle shielding mechanism.
Although U.S. Pat. No. 6,749,588, which is assigned to the same assignee as the present application and which is herein incorporated by reference in its entirety, sets forth many solutions to such problems, other solutions are also desirable. Some solutions employ a projection engaging a recess or undercut to provide an interlock to keep a needle shield retained with a catheter hub, but these solutions can require detailed or intricate molding or manufacturing.